2012年2月27日 星期一

Air Pollution Linked to Heart and Brain Risks

Keith Meyers/The New York TimesA layer of smog rests over Lower Manhattan.

It may be time to start paying more attention to those local air pollution alerts.

That is the message of three new studies this week that found, collectively, that people exposed to higher levels of air pollution have a greater risk of stroke, heart attacks and cognitive deterioration.

The impact of pollution on the heart and brain was seen over both the short and the long term. One nationwide study that followed nearly 20,000 women over a decade found that breathing in levels of polluted air like those commonly found in most parts of the country greatly accelerates declines in measures of memory and attention span. Another study in Boston found that on days when concentrations of traffic pollutants went up, so did the risk of stroke. The odds climbed by more than 30 percent even on days classified by the federal air quality index as “moderate” pollution days, which is intended to correspond to a minimal danger to health.

“At levels that the Environmental Protection Agency says are safe, we’re seeing real health effects,” said Gregory A. Wellenius, an associate professor of epidemiology at Brown University and lead author of the study linking pollution to stroke. “We saw these effects within 12 to 14 hours of when pollution levels went up.”

Studying the links between pollution and health is difficult, since so many factors are involved and it is difficult to establish a direct cause-and-effect relationship. But a link between pollutants in the air and declines in cardiovascular health has been suspected since at least the 1990s, when epidemiological research suggested that breathing in tainted air drives up rates of heart disease. The possible short-term effects of pollution remained particularly unclear, with some studies showing no immediate short-term risk. And little was known about the impact of inhaling emissions and air particles on brain function and dementia.

Dr. Wellenius and his colleagues tried to better clarify the short-term impact of air pollution by studying 1,705 stroke victims admitted to Beth Israel Deaconess Medical Center in Boston from 1999 to 2008, examining medical records to obtain the precise time a stroke actually occurred. They then cross-checked with the Environmental Protection Agency’s air quality index, which rates pollution levels in six general categories, beginning with “good,” then “moderate” and, at the very worst, “hazardous.” Some earlier studies have looked at daily air pollution levels and the number of hospitalizations for ischemic stroke or heart attacks on the same day, but that practice can be deceiving, since people sometimes wait hours or even days before going to a hospital after a stroke. “We were better able to estimate the patients’ air pollution exposure at the time of their stroke,” Dr. Wellenius said.

After controlling for age, hypertension and a slew of other risk factors for stroke, the researchers found a 34 percent higher risk at times when pollution levels climbed from “good” to “moderate.” (In the Boston area, where the study was conducted, pollution levels rarely climb very high, Dr. Wellenius said.) The effect was particularly strong when the researchers looked at levels of so-called black carbon and nitrogen dioxide, two markers of pollution from traffic.

Reducing air pollution levels by just 20 percent, an “achievable” goal, Dr. Wellenius said, “would have prevented about 6,000 of the 184,000 hospitalizations for stroke in the Northeast region” in 2007 alone, he said. The results were published this week in The Archives of Internal Medicine.

In a separate report published Tuesday in The Journal of the American Medical Association, scientists at the University Paris Descartes in France helped bolster the link between short-term exposure to air pollution and cardiovascular disease. They found that a variety of common pollutants — carbon monoxide, nitrogen dioxide, sulfur dioxide and others — raised a person’s immediate risk of having a heart attack.

Breathing in pollutants may cause harm in a number of ways, the researchers noted. They may cause inflammation linked to heart disease, increase the heart rate and thicken the blood, which can cause blood clots and accelerate atherosclerosis, or hardening of the arteries.

The smallest particles of pollution, those finer than 2.5 microns in diameter — or about one-thirtieth the width of a human hair — are particularly effective at infiltrating the body, the researchers noted. There is some evidence that they can even penetrate the brain through the nasal passages, said Jennifer Weuve, the lead author of a third study, also published in The Archives of Internal Medicine, linking pollution to cognitive decline.

Dr. Weuve’s research followed 19,409 women in the United States between the ages of 70 and 81 for about a decade, looking at changes in cognition every two years. Declines in memory and executive function, including the ability to plan and make or carry out a strategy, are normal as people get older. But the study showed that women with higher levels of long-term exposure to air pollution had “significantly” faster declines in cognition than those with less exposure to pollutants.

“Cognitively speaking, this higher exposure is as if you had aged an extra two years,” said Dr. Weuve, an assistant professor at the Rush Institute for Healthy Aging at Rush University Medical Center in Chicago. That might not sound like much, she added, but if there were a treatment “that could just delay the onset of dementia by two years, that would spare the population millions of cases of disease over the next 40 years.”

But they're also kind of delicate. Raspberries in particular seem like they can mold before you even get them home from the market. There's nothing more tragic than paying $4 for a pint of local raspberries, only to look in the fridge the next day and find that fuzzy mold growing on their insides.

Well, with fresh berries just starting to hit farmers markets, you can tell that we Foodlush writers have berries, and how to keep them fresh, on the brain this week! First Jonna shared this excellent tip on how to salvage berries that are starting to lose their luster. Now I'm here to share a tip on how to prevent them from getting there in the first place:

Wash them with vinegar.

A friend of mine shared this tip with me a few weeks ago, and it really, really works. When you get your berries home, prepare a mixture of one part vinegar (white or apple cider probably work best) and ten parts water. Dump the berries into the mixture and swirl around. Drain, rinse if you want (though the mixture is so diluted I find you can't taste the vinegar,) and pop in the fridge.

The vinegar kills any mold spores and other bacteria that might be on the surface of the fruit, and voila! Raspberries will last a week or more, and I've had strawberries go almost two weeks without getting moldy and soft. So go forth and stock up on those pricey little gems, knowing they'll stay fresh as long as it takes you to eat them.

LASIK or Lasik (laser-assisted in situ keratomileusis), commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, ...

Intraoperative complications

The incidence of flap complications has been estimated to be 0.244%.[60] Flap complications (such as displaced flaps or folds in the flaps that necessitate repositioning, diffuse lamellar keratitis, and epithelial ingrowth) are common in lamellar corneal surgeries[61] but rarely lead to permanent visual acuity loss; the incidence of these microkeratome-related complications decreases with increased physician experience.[62][63] According to proponents of such techniques, this risk is further reduced by the use of IntraLasik and other non-microkeratome related approaches, although this is not proven and carries its own set of risks of complications from the IntraLasik procedure.

A slipped flap (a corneal flap that detaches from the rest of the cornea) is one of the most common complications. The chances of this are greatest immediately after surgery, so patients typically are advised to go home and sleep to let the flap heal. Patients are usually given sleep goggles or eye shields to wear for several nights to prevent them from dislodging the flap in their sleep. A faster operation may decrease the chance of this complication, as there is less time for the flap to dry.

Flap interface particles are another finding whose clinical significance is undetermined.[64] A Finnish study found that particles of various sizes and reflectivity were clinically visible in 38.7% of eyes examined via slit lamp biomicroscopy, but apparent in 100% of eyes using confocal microscopy.[64]

The incidence of dry eye varies widely from research studies. A study by Hovanesian et al. reported that 48% of patients experienced dry eye symptoms at 6 months period post surgery.[65]

The incidence of diffuse lamellar keratitis (DLK),[66] also known as the Sands of Sahara syndrome, has been estimated at 2.3%.[67] DLK is an inflammatory process that involves an accumulation of white blood cells at the interface between the LASIK flap and the underlying corneal stroma. It is most commonly treated with steroid eye drops, and sometimes it is necessary for the eye surgeon to lift the flap and manually remove the accumulated cells.

The incidence of infection responsive to treatment has been estimated at 0.4%.[67]Infection under the corneal flap is possible. It is also possible that a patient has the genetic condition keratoconus that causes the cornea to thin after surgery. Although this condition is screened in the preoperative exam, it is possible in rare cases (about 1 in 5,000)[citation needed] for the condition to remain dormant until later in life (the mid-40s). If this occurs, the patient may need rigid gas permeable contact lenses, Intrastromal Corneal Ring Segments (Intacs),[68] Corneal Collagen Crosslinking with Riboflavin[69] or a corneal transplant.

The incidence of persistent dry eye has been estimated to be as high as 28% in Asian eyes and 5% in Caucasian eyes.[70] Nerve fibers in the cornea are important for stimulating tear production. A year after LASIK, subbasal nerve fiber bundles remain reduced by more than half.[71] Some patients experience reactive tearing, in part to compensate for chronic decreased basal wetting tear production.

The incidence of subconjunctival hemorrhage has been estimated at 10.5%[67] (according to a study undertaken in China; thus results may not be generally applicable due to racial and geographic factors).

Glare is another commonly reported complication of those who have had LASIK.[20]

Halos or starbursts around bright lights at night are caused by the irregularity between the lasered part and the untouched part. It is not practical to perform the surgery so that it covers the width of the pupil at full dilation at night, and the pupil may expand so that light passes through the edge of the flap into the pupil.[72] In daytime, the pupil is smaller than the edge. Modern equipment is better suited to treat those with large pupils, and responsible physicians will check for them during examination.

Late traumatic flap dislocations have been reported 1–7 years post-LASIK.[73]

Dry eye or in severe cases Chronic Dry eye. Due to nerves that are severed during the Lasik operation (around 70% of corneal nerves are severed), the lubrication system of the eye is affected and nerves may never recover to pre-operative condition. This may leave the patient with potential permanent dry eyes.

LASIK and other forms of laser refractive surgery (i.e. PRK, LASEK and Epi-LASEK) change the dynamics of the cornea. These changes make it difficult for your optometrist and ophthalmologist to accurately measure your intraocular pressure, essential in glaucoma screening and treatment. The changes also affect the calculations used to select the correct intraocular lens implant when you have cataract surgery. This is known to ophthalmologists as "refractive surprise." The correct intraocular pressure and intraocular lens power can be calculated if you can provide your eye care professional with your preoperative, operative and postoperative eye measurements.

Although there have been improvements in LASIK technology,[74][75][76] a large body of conclusive evidence on the chances of long-term complications is not yet established. Also, there is a small chance of complications, such as haziness, halo, or glare, some of which may be irreversible because the LASIK eye surgery procedure is irreversible.

Although the cornea usually is thinner after LASIK, because of the removal of part of the stroma, refractive surgeons strive to maintain the maximum thickness to avoid structurally weakening the cornea. Decreased atmospheric pressure at higher altitudes has not been demonstrated as extremely dangerous to the eyes of LASIK patients. However, some mountain climbers have experienced a myopic shift at extreme altitudes.[79][80]

In situ keratomileusis effected at a later age increases the incidence of corneal higher-order wavefront aberrations.[81][82] Conventional eyeglasses do not correct higher order aberrations.

Microfolding has been reported as "an almost unavoidable complication of LASIK" whose "clinical significance appears negligible."[64]

Blepharitis, or inflammation of the eyelids with crusting of the eyelashes, may increase the risk of infection or inflammation of the cornea after LASIK.[citation needed]

Myopic (nearsighted) people who are close to the age (mid- to late-forties) when they will require either reading glasses or bifocal eyeglasses may find that they still require reading glasses despite having undergone refractive LASIK surgery. Myopic people generally require reading glasses or bifocal eyeglasses at a later age than people who are emmetropic (those who see without eyeglasses), but this benefit may be lost if they undergo LASIK. This is not a complication but an expected result of the physical laws of optics. Although there is currently no method to completely eradicate the need for reading glasses in this group, it may be minimized by performing a variation of the LASIK procedure called "slight monovision." In this procedure, which is performed exactly like distance-vision-correction LASIK, the dominant eye is set for distance vision, while the non-dominant eye is set to the prescription of the patient's reading glasses. This allows the patient to achieve a similar effect as wearing bifocals. The majority of patients tolerate this procedure very well and do not notice any shift between near and distance viewing, although a small portion of the population has trouble adjusting to the monovision effect. This can be tested for several days prior to surgery by wearing contact lenses that mimic the monovision effect. Recently, a variation of the laser ablation pattern called PresbyLASIK, has been developed to reduce or eliminate dependence on reading glasses while retaining distance vision

Related Stories

A drug that can extend the life of men with advanced prostate cancer by more than three months has provisionally been rejected for NHS use.

The health watchdog for England and Wales says the drug's benefits are not enough to justify the price the NHS has been asked to pay.

Cancer charities have been angered by the decision about abiraterone, one of the few drugs available to men in the final stages of prostate cancer.

A final decision is yet to be made.

Prostate cancer is the most common cancer to affect men in the UK.

The chief executive of the National Institute for Health and Clinical Excellence (NICE), Sir Andrew Dillon, said the drug was effective, and one of its key benefits was that it could be taken orally in the patient's own home.

"We are therefore disappointed not to be able to recommend it for use on the NHS, however it is an expensive drug," Sir Andrew added.

'Bitter blow'

Abiraterone costs just under £3,000 for one month's supply but has been offered at a undisclosed discounted price to the NHS.

Cancer charities have criticised the health regulator's decision.

"Quite simply, abiraterone prolongs the life of men with incurable prostate cancer. The draft decision is a bitter blow to thousands of men and their families and must be overturned," said Owen Sharp, chief executive of The Prostate Cancer Charity.

Case study: Ron McCoo, Blackpool

Ron, 59, was diagnosed with prostate cancer in 2010. He has been using abiraterone for three months. His local health provider currently allows the drug to be used on an individual basis. He says it has changed his life.

"I have my life back. I have a lot more energy and no pain. My quality of life is excellent. I wouldn't even know I have cancer now, it's that good.

"I know it doesn't work for everybody but it certainly works for me. I would be devastated if it was no longer available on the NHS."

Ron's wife Terri says: "We know NICE has to take a lot of things into consideration, but when you have a terminal illness an extra fourth months is very precious."

Prof Peter Johnson, Cancer Research UK's chief clinician, said: "Only one other drug is available on the NHS that has been shown to prolong survival but it has more severe side-effects than abiraterone and is effective in fewer men."

Cancer Research UK, which provided support in the development of the drug and could benefit from its royalties, said it believed that NICE might have overestimated the number of people who needed the drug.

It said that if the regulator rethought the criteria used to calculate the cost-effectiveness of the drug, there is a chance it could be made available under special arrangements for treating people at the end of their lives.

NICE said it had already used the appropriate methods in its review, and concluded that the number men who would need the drug was too large to consider such agreements.

Almost 500 men have successfully applied for abiraterone in the past nine months through the alternative route of the Cancer Drugs Fund in England, an initiative designed to increase access to drugs.

Until final guidelines are issued by the health regulator, decisions can continue to be made locally about the use of abiraterone.

Each year 37,000 men are diagnosed with prostate cancer, and more than 10,000 die from it.

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